JPH03284329A - Ceramic membraneous filter and production thereof - Google Patents

Abstract

PURPOSE:To obtain a ceramic membraneous filter having high filtering efficiency by forming a middle layer with a ceramic material made of particles having a prescribed particle size range classified by elutriation as starting material. CONSTITUTION:At least one side of a porous substrate is coated with a porous middle layer having a smaller average pore diameter than the substrate and one side of the middle layer is coated with a filter membrane having a smaller average pore diameter than the middle layer to obtain a ceramic membraneous filter. The middle layer is formed with a slurry of a ceramic material made of particles having a prescribed particle size range classified by elutriation as starting material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ceramic membrane filter used as an ultrafiltration membrane, a precision filtration membrane, etc.

(Prior art) In filtration membranes used in various fields, mechanical strength,
Ceramic membrane filters have excellent heat resistance and corrosion resistance. In order to reduce the flow resistance of the fluid to be treated as much as possible, such ceramic membrane filters have a small number of porous supports with large pores (both have a multilayer structure with a thin filtration membrane fixed to the side surface). Generally speaking, the above-mentioned filtration membrane is appropriately selected depending on the type of fluid to be treated.

In the ceramic membrane filter applied to ultrafiltration membranes, precision filtration membranes, etc. targeted by the present invention, a membrane having an average pore diameter of 100 OA or less is selected as the filtration membrane.

Therefore, in order to form a filtration membrane with an average pore size of 100 OA or less, i! @2 of the average pore diameter of the membrane
A slurry of ceramic raw material with fine particles having a particle size of ~5 times as large is used, but since the particle size of the fine particles in this slurry is extremely small, at least one side of the porous support is coated with an average finer particle than that of the support. In many cases, a porous intermediate layer with a small pore size is formed, and the above-mentioned filtration membrane is formed on one side of the intermediate layer.

(Problem to be Solved by the Invention) Incidentally, the particle groups constituting the ceramic raw material have a wide particle size distribution, and even if a ceramic raw material with a predetermined average particle size is used as the raw material for the intermediate layer, the particle groups on the small diameter side It is difficult to form an intermediate layer having a predetermined permeability due to the influence of the particles, and it is also difficult to form an intermediate layer suitable for forming a filtration membrane due to the influence of the large-diameter particle group. For this reason, it is preferable to use ceramic raw materials with a sharp particle size distribution.
Such ceramic raw materials are expensive and economically disadvantageous. It is therefore an object of the present invention to address such problems.

(Means for Solving the Problems) The present invention relates to a ceramic membrane filter and a method for manufacturing the same, and a first aspect of the present invention is to provide a porous support with pores on at least one side thereof having a smaller average pore diameter than that of the support. The ceramic membrane filter is a ceramic membrane filter comprising a quality intermediate layer and a filtration membrane having a smaller average pore size than the intermediate layer on one side of the intermediate layer, and the intermediate layer contains elutriated particles having a particle size within a predetermined range. The second invention is a method for manufacturing the ceramic membrane filter, in which the intermediate layer is classified by elutriation and has a particle size within a predetermined range. It is characterized in that it is formed using a slurry made of particles.

In the present invention, the porous support is a pipe, monolith, honeycomb, or plate made of inorganic particles such as alumina, zirconia, titania ceramics, glass such as borosilicate glass, metal such as nickel, or a sintered body of carbon. It has a single-layer structure or a multi-layer structure of two or more layers. The porous support has the lowest possible flow resistance when the fluid to be treated passes through it, and has an average pore diameter of several μ■ to several tens of micrometers.
It is about 0μ in size.

In the present invention, the intermediate layer is a porous layer made of ceramic material, and is obtained by coating at least one side of a porous support with a slurry of alumina, zirconia, titania, silica, etc. and sintering the slurry.

Since a filtration membrane is formed on one side of the intermediate layer, it is necessary to have an average pore diameter smaller than the average pore diameter of the porous support described above, and the average pore diameter of the intermediate layer is 0
It is about 1 μm to several tens of micrometers.

In addition, such an intermediate layer may be a single layer or two layers similar to the porous support.
It has a multilayer structure with more than one layer, and in the case of a single layer, the intermediate layer itself, and in the case of a multilayer structure, at least the layer on the porous support side (first intermediate layer) has been subjected to elutriation classification. The raw material is a ceramic material consisting of particles with a particle size within a predetermined range, and a slurry obtained by elutriation classification is used.

In the present invention, the filtration membrane has an average pore diameter of 18 to 1.
It has a pore diameter in the extremely small range of 000 A, and is made by firing a thin film of alumina, zirconia, titania, silica, etc., which is formed on one side of the intermediate layer using a slurry or sol solution. .

The elutriation classification used in the present invention is known per se, in which crude ceramic raw materials are made into a slurry using a dispersant and a deflocculant and left in a container for a predetermined period of time. By removing a certain slurry precipitate, a ceramic material consisting of particles with a predetermined range of particle sizes is obtained.

(Operations and Effects of the Invention) In the ceramic membrane filter according to the present invention, since the intermediate layer is made of a ceramic material consisting of particles having a particle size within a predetermined range and agglomerated particles are removed, fine particles in the intermediate layer are formed. The pore size is distributed in a narrow range centered on the average pore size, and an intermediate layer is formed that has a predetermined permeability and has good film formation properties for the filtration membrane, and due to this intermediate layer, it has excellent filtration performance. Moreover, a ceramic membrane filter with a smooth membrane surface can be obtained.

In addition, since the intermediate layer is generally formed using a slurry, the process of preparing a slurry of ceramic material is essential for forming the intermediate layer, and elutriation classification can be performed in this preparation process. The raw material with a wide range of ffL weight distribution obtained by classification is cheaper than the raw material which is prepared in advance into the form of fine powder with a narrow particle size distribution, and is extremely economically advantageous.

(Example) In this example, a support with a monolithic structure is adopted as the porous support, a first intermediate layer is formed on the circumferential surface of each inner hole of the support, and a first intermediate layer is further formed on the circumferential surface of the intermediate layer. 2 form an intermediate layer,
A ceramic membrane filter in which a filtration membrane is formed on the surface of the second intermediate layer will be exemplified. Note that each of these intermediate layers and filtration membranes are formed by coating a slurry of ceramic raw materials.

(1) Coating device A coating device shown in FIG. 1 was used for coating the slurry. The coating equipment is disclosed in Japanese Patent Application Laid-Open No. 61-2
This device is similar to the device shown in Japanese Patent No. 38315, and includes a holding mechanism 10a for a cylindrical porous support A (including one provided with an intermediate layer) in a pressure vessel 11. The holding mechanism 10a includes a pair of upper and lower support plates 12a, 12b and a plurality of connecting bolts 13a, 13b, . . . , and these connecting bolts 13a, 13b, .

By connecting the support plates 12b to each other, the support body A is held between both support plates 12a and 12b. A supply vibrator 15a that connects to the tank 14 containing the coating liquid is connected to the lower support plate 28, and the vibrator 158 opens at the lower end of the support A and enters the tank 14 by driving the supply pump 15b. A coating liquid is supplied to support A.

A discharge vibrator 15c is connected to the supply vibrator 15a, and the discharge vibrator 15c discharges the coating liquid in the support A into the tank 14 after the coating operation is completed.

On the other hand, an outflow vibrator 16a facing above the tank 14 is connected to the upper support plate 12b, and the vibrator 16a opens at the upper end of the support A and allows the coating liquid overflowing from the support A to flow back into the tank 14. . Further, an exhaust vibrator 17b connected to a vacuum pump 17a is connected to the upper part of one side of the pressure vessel 11, and the pressure inside the pressure vessel 11 is reduced to a desired pressure by driving the vacuum pump 17a. A water meter 17c is attached to one side of the pressure vessel 11, and the water meter 17c indicates the amount of water that passes through the support A and flows into the pressure vessel 11 during the coating operation.

In the coating apparatus 1o, the outflow vibrator 16
The coating liquid is supplied into the support body A by driving the pump 15b with the throttle valve 16t+ of the unit a fully open, and when the coating liquid reaches the upper end of the support body A, the vacuum pump 17a is driven. The pressure inside the pressure vessel 11 is reduced, and the throttle valve 16b is throttled by a predetermined amount to circulate the coating liquid upwardly within the support A under pressure. This creates a pressure difference between the inside and outside of the support A, and due to this pressure difference, moisture in the coating liquid permeates through the support A and flows into the pressure vessel 11. During this time, the intermediate layer or filtration membrane in the coating liquid Components are supported on the inner circumferential surface of support A. Note that since the thickness of the coating layer or membrane is proportional to the amount of water flowing into the pressure vessel 11, the thickness is adjusted based on the amount of water displayed by the water meter 17c. When the thickness reaches a predetermined thickness, the supply pump 15b is stopped, the throttle valve 16b is fully opened, and the on-off valve 15d of the drainage vibrator 15C is opened, and dehydration is then carried out for several minutes under reduced pressure, and the vacuum pump 17a is opened. Stop the drive.

As a result, the coating liquid in the support body A is discharged into the tank 14 through the discharge vibrator 15c, and the coating operation is completed.

In this example, this coating method is referred to as a dynamic pressure vacuum method.

(2) Porous support A Porous support A has an external shape with an outer diameter of 30mm and a length of 1000++m, and has a monolithic structure with 19 inner holes with a diameter of 4+ni extending in parallel in the length direction. It is a sintered body of an extruded product mainly composed of alumina with an average particle size of 30 μm, and has a maximum pore size of 7 μm.

(3) Moisture and ammonium polycarboxylate, which is a dispersant, are added in predetermined amounts to the ceramic powder that is the raw material for Kibushi classification, mixed in a ball mill, diluted in a predetermined container, stirred, and then diluted. The liquid is allowed to stand for a predetermined period of time, and then the upper liquid (upper liquid) from a predetermined height above the bottom of the container,
The precipitate is separated from the lower part from this position and taken out.

(4) Intermediate layer B In this example, the intermediate layer B has a two-layer structure of the first intermediate layer b1 and the second intermediate layer b2, and the precipitate classified in this section is used as the raw material for the first intermediate layer b1.

First intermediate layer b1: A slurry was prepared using Al2O3 powder with an average particle size of 4μ as a crude raw material and 301t70wt% of a crude raw material containing 0.5wt% of ammonium polycarboxylate as a dispersant. After thorough stirring, the mixture was allowed to stand for each hour. Using the obtained supernatant liquid or precipitate, 0.3vt of Ti02 (average particle size □1 μm), which is a sintering aid, was added to the solid content.
% and mix. Using this as a raw material, the water content is 95%
A slurry consisting of was prepared. Each slurry obtained was coated on the circumferential surface of each inner hole of the porous support A using a dynamic pressure vacuum method, and after drying, it was fired at 1500"C to form a first intermediate layer having a thickness of 170 μm. The properties of the resulting laminate of the porous support A and the first intermediate layer b1 are shown in the attached table.

In addition, in the dynamic pressure vacuum method, the support is boiled in water for 3 hours to defoam before coating, and the pressure vessel 1 is
The degree of vacuum inside 1 is 730mmHg to 740++mHg.

The liquid pressure of the slurry against the inner peripheral surface of the support is 2 kg/cm.
2. The fluid contact time is 1 minute 20 seconds, and
After discharging the slurry, it was dehydrated under reduced pressure for S minutes under the vacuum described above.

The same applies to the dynamic pressure vacuum method described below.

Second intermediate layer b2: average particle size of 05 μm, purity of 99.5vt% Al+03 powder, and 0.5vt of ammonium polycarboxylate as a peptizer.
%, and 4 t% of polyacrylic acid as a binder was added to prepare a slurry with a moisture content of 95 t%, and this slurry was applied to the inner circumferential surface of the first intermediate layer b1 by a dynamic pressure vacuum method without aqueous classification. It was coated. Next, after drying this, 1500
C. to form a second intermediate layer 1b2 having an average pore diameter of 02 .mu.m and a film thickness of 5.mu.m. Obtained porous support A
, the characteristics of the laminate of the first intermediate layer b1 and the second intermediate layer b2 are shown in the attached table.

The reason for forming the second middle open layer b2 in this example is as follows. That is, since the average pore diameter of 1μ■ of the first intermediate layer b1 is larger than the average vL diameter <0.2μ■ of the slurry used for the d-filtration membrane described later, it is possible to improve the film formability of the filtration membrane. This is to close pores and cracks on one side that are extremely large compared to the average pore diameter that may be formed in the ai5 film.

(5) Using TiO2 powder with an average particle size of filtration membrane <02μl as a crude raw material, prepare a slurry consisting of 2vt% of the raw material containing 4wt% of ammonium polycarboxylate as a dispersant and 98wt% of water, and thoroughly After stirring, the mixture was allowed to stand for 20 hours, and the resulting slurry was used to prepare a slurry with a moisture content of 99.2 vt%. This slurry was coated on the circumferential surface of the second intermediate layer b2 using a dynamic pressure vacuum method, and after drying, it was fired at 8oo''C to form a filtration membrane with an average pore diameter of O, OSμ, and a film thickness of 5μ. Formed.

(6) Characteristics of ceramic membrane filter Dextran with a molecular weight cut-off of 230,000 is used as the liquid to be treated.
Using a 00pp++ solution, this treated liquid was circulated and supplied to a filter equipped with each ceramic membrane filter, and the circulation flow rate was 2 m.
Cross-flow filtration was performed for 7 seconds at a pressure of 1 kg/cm2 for 60 minutes, and the rejection rate (%) was calculated using the formula below, as well as the amount of permeable i5 liquid. /cm2 for 60 minutes for regeneration, and then cross-flow filtration was performed in the same manner as above, and the rejection rate and amount of permeated liquid were calculated.

Note *: Measure the amount of dextran in the liquid using a TOC measuring device (7) Measurement average particle size of each characteristic: Measured with Sedigraph manufactured by Shimadzu Corporation (average particle size 50% Diameter) Average pore diameter: Measured by underwater foaming method Membrane surface roughness 2 Ra... 10 point average roughness, Rz... Center line average roughness (8) Discussion For each ceramic membrane filter, it is clear from the attached table. N
Among O31 to N010, the average particle size of the crude raw material is 4.0 μ■
(No. 11 uses a slurry of crude raw materials) Properly classified with a water brush and has an average particle size similar to No. 3 to
In case of N015, the dextran rejection rate is the same as that of NO,11 which uses a slurry of crude raw material, and the amount of permeate is significantly large. This is true for N013~NO
This means that the ceramic membrane filter of No. 5 is a filter with high filtration efficiency. NO33NO07 and NO
The particle size distribution of the particles in the slurry used in Example No. 11 is shown in the graph of FIG.

(Margin below) / /

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a coating apparatus for coating slurry, and FIG. 2 is a graph showing the particle size distribution of particles in the slurry. Explanation of symbols 10...Coating device, 11...Pressure vessel, 1
2a, 12b... Support plate, 14... Tank, 15b
... Supply pump, 17a... Vacuum pump.

Claims (2)

[Claims] (1) At least one side of a porous support is provided with a porous intermediate layer having an average pore diameter smaller than that of the support, and one side of the intermediate layer is provided with a filtration membrane having an average pore diameter smaller than that of the intermediate layer. 1. A ceramic membrane filter characterized in that the intermediate layer is made of a ceramic material made of elutriated particles having a particle size within a predetermined range. (2) A method for manufacturing a ceramic membrane filter according to item 1, characterized in that the intermediate layer is formed from a slurry of a ceramic material made of elutriated particles having a particle size within a predetermined range. Method for manufacturing membrane filters.